Physics MCQs
Topic Notes: Physics
MCQs and preparation resources for competitive exams, covering important concepts, past papers, and detailed explanations.
Plato
- Biography: Ancient Greek philosopher (427–347 BCE), student of Socrates and teacher of Aristotle, founder of the Academy in Athens.
- Important Ideas:
- Theory of Forms
- Philosopher-King
- Ideal State
61
Why does a cricket fielder pull their hands backward while catching a fast-moving ball?
Answer:
Because he experiences less force over a longer period of time
By moving their hands backward, the fielder increases the time taken to bring the ball to rest. Since force is the rate of change of momentum (F = Δp/Δt), increasing the time interval (Δt) reduces the average force (F) exerted on the fielder's hands, preventing injury.
62
Linear momentum is defined as the product of which two physical quantities?
Answer:
mass × velocity
Linear momentum (p) is a vector quantity defined as the product of an object's mass (m) and its velocity (v). It represents the quantity of motion an object possesses. The SI unit for momentum is kilogram-meters per second (kg·m/s).
63
The rate of change of linear momentum of an object is directly proportional to which of the following?
Answer:
Applied force
Newton's Second Law of Motion states that the net force acting on an object is equal to the rate of change of its momentum. Mathematically, F = dp/dt. Therefore, the rate of change of momentum is directly proportional to the applied net force acting on the body.
64
Calculate the momentum of an object with a mass of 10 kg moving at a velocity of 2 m/s.
Answer:
20 kgms-1
Momentum (p) is defined as the product of an object's mass (m) and its velocity (v), expressed by the formula p = mv. Given a mass of 10 kg and a velocity of 2 m/s, the calculation is 10 kg * 2 m/s = 20 kg·m/s. This represents the quantity of motion an object possesses.
65
Why does a cricket player pull their hands backward while catching a fast-moving ball?
Answer:
Momentum
By pulling their hands backward, the fielder increases the time interval over which the ball's momentum is reduced to zero. According to Newton's second law, force is the rate of change of momentum. By increasing the time of impact, the fielder reduces the average impulsive force exerted on their hands, thereby minimizing the risk of injury and making the catch easier to secure.
66
A metal ball and a rubber ball of equal mass strike a wall at the same velocity. The rubber ball bounces back, while the metal ball does not. Which ball experiences a greater change in momentum?
Answer:
The rubber ball suffers greater change in momentum
Change in momentum is Δp = mv_final - mv_initial. For the metal ball, Δp = 0 - (-mv) = mv. For the rubber ball, assuming an elastic collision, Δp = mv - (-mv) = 2mv. Thus, the rubber ball experiences a larger change in momentum.
67
A 20 g bullet is fired from a 5 kg gun with a muzzle velocity of 100 m/s. What is the recoil velocity of the gun?
Answer:
-0.4 ms-1
Using the law of conservation of momentum, the initial momentum of the system (gun + bullet) is zero. Thus, the final momentum must also be zero: (m_bullet * v_bullet) + (m_gun * v_gun) = 0. Converting 20 g to 0.02 kg, we get (0.02 * 100) + (5 * v_gun) = 0. Solving for v_gun gives 2 + 5 * v_gun = 0, resulting in v_gun = -0.4 m/s.
68
Which physical properties determine the momentum of an object?
Answer:
both its mass and velocity
Linear momentum is a fundamental vector quantity in physics defined as the product of an object's mass and its velocity (p = mv). Therefore, both the mass of the object and its velocity are the essential factors that determine the magnitude and direction of its momentum.
69
Determine the momentum of an object with a mass of 85 kg moving at a velocity of 60 ms-1.
Answer:
5,100 kg ms-1
Momentum (p) is defined as the product of an object's mass (m) and its velocity (v), expressed by the formula p = m * v. Substituting the given values, p = 85 kg * 60 ms-1 = 5,100 kg ms-1. Momentum is a vector quantity that describes the quantity of motion an object possesses, which is a crucial concept in analyzing collisions and dynamical systems.
70
Which physical quantity shares the same dimensions as impulse?
Answer:
Momentum
Impulse is defined as the change in momentum (J = Δp). Since both represent the product of force and time (or mass and velocity), they share identical dimensions of [M L T^-1].